1. Field of the Invention
This invention relates broadly to video imaging apparatus. More particularly, this invention relates to video imaging apparatus including an improved low-resolution solid-state video camera having a quantized image array of either linear or area pixels for producing a photogenerated video output signal. Solid-state video cameras referred to herein include charge injection devices (CID), charge coupled devices (CCE) or photodiode (PD) devices.
2. Description of the Prior Art
Commercial solid-state video cameras are both reliable and inexpensive video imaging apparatus but have one drawback. The size of state-of-the-art pixel arrays is limited, thus classifying them as low-resolution type. Because of this limitation, they cannot be used to provide high-resolution information where high-accuracy (0.1% or better) dimensional measurements are required of objects in a wide field of view.
Prior art detection techniques for object outline and edge position, while satisfactory for their intended purpose, have not proved workable in solving the aforesaid problems with low-resolution, noisy, solid-state video camera output signals. In one type of camera, the video output signal is level detected to determine in which photo element represented by a pixel pulse the step of illuminating an object edge occurs. Low-resolution pixel pulses are often indefinative because of their irregular pulse slope and therefore not very susceptible to accurate level detection. In another type of camera, the pixel pulse level representing an object edge may vary from below a minimum to a maximum level, depending upon illumination level of the object, thus detracting from the level detecting technique. Additional prior art differentiating and zero crossing detection techniques, as well as computer statistical analysis techniques, have been tried to precisely detect object outline and edge position but either did not work satisfactorily or was too expensive for on-line applications.